Instrument type relay



July 3, .1962 E. M. EADIE, JR

INSTRUMENT TYPE RELAY 2 Sheets-Sheet 1 Filed June 4. 1959 INVENTOR.

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y 3, 1962 E. M.EADIE, JR 3,042,840

INSTRUMENT TYPE RELAY Filed June 4, 1959 2 Sheets-Sheet 2 IN VEN TOR. 12 zamanz MZ'aQ'iefi/it,

Alia 2W5] A United States atent ffice 3,042,849 Patented July 3., 1962 This invention relates to highly sensitive instrument relays and more particularly to relays of the load-currentcontact-aiding type which include two pairs of contacts, 'one of which is of the magnetic type.

Electrical instrument type mechanisms which include a winding which is adapted for connection to a small electrical output device, such as a photoelectric cell, thermocouple, and the like, develop only small mechanical forces which generally are not of sufiicient magnitude to effect reliable engagement of relay circuit contacts associated with such mechanisms. Known systems for developing additional torque in the instrument moving system to insure reliable relay contact closure include the use of multiple contacts and a moving system having a second power,

or auxiliary, winding in addition to the winding connected to the photoelectric cell, or the like. The relatively large relay load current is made to flow through the second winding of the instrument following initial relay contact closure to supply additional torque to the instrument moving system for aiding the relay contact closure. Such relays are referred to as load-current-contact-aiding type relays and are well known in the prior art. It will be quite apparent that in a load-current-contact-aiding type relay, an initial contact must be made before the contact can be improved. Such relays are generally rather unreliable, particularly when the relay has remained inoperative for a long period of time and/or when the relay is subject to conditions promoting the formation of high resistance films on the contact elements. The small contact pressure, particularly at low voltages, does not always provide a reliable initial closure, and without a contact closure, there can be no improved closure by a loadcurrent-contact-aiding arrangement. The load-currentcontact-aiding relay is simply reset by opening the load current circuit to thereby break the current to the auxiliary relay winding.

A second known method for insuring a reliable nonchattering contact closure includes the use of magnetic contacts wherein a magnetized membercomprises one contact element While the associatedcontact element is made of magnetic material. The moving system of the instrument displaces one of the contact elements attached thereto until the intercontact distance reaches a critical value at which the magnetic attraction between the contacts 'displac'es'he moving system, and the contacts then engage under magnetic attraction to aiiord a reliable nonchattering contact closure.

With prior art magnetic contact type relays, some form of resetting mechanism for separating the closed contacts is required since the torque developed by the control current is usually of an order substantially lower than the force resulting from the magnetic attraction of the engaged magnetic contacts. 7 Prior art resetting arrangements include various mechanical type mechanisms. Also,

' vention.

contact to neutralize the magnetic field thereof. Further resetting arrangements include passing a relatively high resetting current pulse through the moving coil in a direction opposite to that traversed by the control current. All such prior art resetting arrangements inherently complicate the relay construction and often are impractical and/ or unreliable.

In the sensitive instrument type relay of my invention I combine the above described load-current-contact-aiding arrangement with the magnetic contact type to obtain the benefits of such type but without the .inherent shortcomings of each. That is, I utilize the magnetic type contacts to provide reliable initial contact closure, and the load-current-contact-aiding arrangement to improve such initial contact. No exterior resetting mechanism is necessary since the construction includes novel means whereby a contact separation is effected'by merely opening the load current circuit, as in a conventional load-current-contactaiding type system. I

An object of this invention is the provision of a loadcurrent-contact-aiding type relay which includes also magnetic contacts.

An object of this invention is.the provision of a novel relay contact system for a load-current-contact-aiding type relay which system includes one pair of magnetic type contacts for making reliable initial contact and a second pair of contacts which includes a flexible contact member for suflic ient wiping action during closure therevof for reliable final contact closure and which contacts may be reset simply by breaking the load-current.

' An object of this invention is the provision of a loadcurrent-contact-aiding type relay which operates reliably :at very low voltages.

note like parts in the several views;

FIGURE 1 is a fragmentary plan view of an instrument type relay embodying my invention and included in a schematic circuit arrangement;

FIGURE 2 is a side view as seen from the right in FIGURE 1;

FIGURE 3 is a viewwhich is similar to FIGURE 1 only showing the position of the contacts at the initial closure of the magnetic contact elements;

FIGURE 4 is a view which is similar to FIGURE 3 only showing the contacts in the final stage of closure; FIGURE 5 is a view which is similarto FIGURE 3 only showing the contacts during a contact separating, or reset, stage of operation; and

FIGURE 6 is a fragmentary plan view of an instrument type relay embodying a modified form of my in- Reference is first made to FIGURE 1 of the drawings wherein reference numeral 10 identifies the pivotable coil of the movingsystem of an instrument type relay which A includes a magnetic system, not shown, having a magnetic flux gap in which the coil is supported for pivotal movement. The instrument is of the well known load-currentcontact-aiding type wherein the coil comprises a pair of coil sections, one of which is shown connected through lead wires 11 and 12 to a variable control current source 13 that develops only a small current flow through the coil section of the order of a few micro-amperes, for example. For purposes of illustration, the current source 13 is shown diagrammatically as a thermocouple, but is to be understood that such source may comprise a photoelectric cell or the like.

A pointer 14 mounted on the coil and rotatable with the coil, is adapted to cooperate with a scale 16 formed on a scale plate, not shown. A small rider or contact element 17 of magnetic material is secured adjacent the outer end of the pointer 14 for cooperation with a relatively stationary magnetic contact element 18. The magnetized contact element 18 is so positioned that contact element 17 is drawn into engagement therewith when the pointer 14 has rotated in a clockwise direction to a predetermined graduation on the scale 7 by the flow of control current from the thermocouple 13 through the control winding section of the coil 10'.

The pointer shaft 14 comprises relatively stiif arm portions 14a and 14b joined by a very flexible section 140. In the drawings, the flexible section 140 is shown com prising a flexible helical coil element secured, for example, by several tight turns at the ends thereof to the relatively stiffer sections 14a and 14b. Such a pointer construction is illustrated in the Patent No. 2,494,622 which issued January 17, 1950, to A. H. Lamb. It will here be understood, however, that the construction of the pointer 14 is not limited to the use of flexible helical coil section 140 therein since the desired flexibility may be achieved by other means, such as by utilizing a unitary pointer member 14 which includes a length at 140 of reduced cross sectional area to provide greater flexibility thereat.

A second contact element 21 is secured as by welding, or any other suitable means, to the pointer 14 at the section 14a adjacent the coil 10. The secondary contact element 21 extends upwardly and at an angle with the pointer 14. Such secondary contact element cooperates with a second relatively stationary contact element 22 which is shown electrically connected to the magnetic contact element 18. The elongated secondary contact element 21 is made from suitable contact material such as platinum-iridium alloy, or the like, which is flexible whereby a wiping action is obtained between the contact elements 21 and 22 upon relative movementthereof when engaged. The pointer 14 and contact element 21 are resilient and return to a normal predetermined position, shown in FIGURE 1, when the relay contacts are open.

It will be seen that the contact elements 17 and 21 are connected together, as well as the contact elements 18 and 22. A load circuit which includes a series connected current source 26, reset switch 27 and load device 28, is connected through the power winding, or auxiliary coil, section of the coil 10' and to the connected contact elements 17 and 21 and elements 18 and "22. The load device may comprise a visual or an audible signal, a motor, a power relay, or the like, according to the desired control or relay action. With the switch 27 closed, it will be understood that upon closure of the contacts 17 and 18 and/or the contacts 21 and 22, the load current from the source 26 flows through the auxiliary coil section of the coil 12 to effect the further displacement of the moving system in a clockwise direction, as viewed in FIGURE 1, to thereby improve the contact engagement. Such action results in the provision of the well known load-current-contact-aiding, type of relay system. As in the usual load-currentcontact-aiding type relay, the resetting function is initi- 1 t1. suffering from the inherent defects of the individual systems. Reference is now made to FIGURE 3 wherein the arrangement is shown in a contact-making stage of operation. As mentioned above, when the current from the control current source 13 through the control winding of the coil 10 moves the pointer 14 and rider 17 into proximity to the magnet contact 18, the magnetic attraction thereof snaps the magnetic rider 17 into firm engagement with the said contact 18. At such stage of contact closure, as illustrated in FIGURE 3, the relay contacts 21 and 22 are preferably in the open condition. (However, since the above sequence of contact closure is not essential to satisfactory relay operation, it will be understood that the relay contacts 21 and 22 may be made to close simultaneously with the closure of the magnetic contacts 17 and 18, or even slightly prior to the engagement of the contacts 17 and 18). Because of the impact-engagement provided by the magnetic contacts 17 and 18, the load-current circuit is completed with good initial contact of the contact elements 17 and 18 whereupon a substantially in stantaneous load current of substantial magnitude flows through the auxiliary coil element to provide the moving system with added torque in the contact-closing direction. The additional torque on the moving coil system serves to further rotate the moving coil system and thereby flex, or bend, the pointer 14, as seen in FIGURE 4, and since the helical coil section 140 has the greatest flexibility of the pointer, maximum flexing occurs thereat. This further rotation of the moving coil system provided by the load current flow therethrough, results in the initial closure of the contact elements 21 and 22 (providing, of course, such contacts are not closed simultaneously with the contact elements 17 and 18, or therebefore, as described above) and a wiping, or scraping, action between the flexible contact element 21 and fixed contact element 22.

As is well understood by those skilled in this art, a high resistance film may form on the relay contacts, particularly when the relay has remained inoperative for a long period of time or when the atmospheric conditions are such as to promote the formation thereof. Consequently, although a good contact is provided by the snap action closure of the magnetic contact elements 17 and .18, such closure does not insure the best contact engagement. An improved contact engagement is provided by a wiping, or scraping, contact engagement between contact elements, particularly if one contact element is made of hard material and engages a softer material second contact element along a sharp edge thereof. In the relay of my invention, the reliable (but not always the lowest resistance) contact engagement provided by the magnetic contact elements 17 and 18 is supplemented by the wiping, or scraping action contact between the flexible contact element 21 and the stationary contact element 22. The contact element 22 is preferably made of material such as a rhodium alloy, which material is harder than the contact material of the flexible contact element 21. The scraping, or wiping, action between the contact elements 2 1 and 22 after initial engagement thereof and further rotation of the moving coil system by the flow of load current through the moving coil section, provides a good electrical contact between the elements to thereby insure a maximum load current flow and contact pressure.

A further important feature of my invention resides in the fact that unlike most prior art instrument type relays employing magnetic contact elements, the relay of my invention is reset by merely opening the switch 27 to break the flow of load circuit current through the auxiliary movable coil section. As seen in FIGURE 4, both the pointer 14 and contact element 21 are flexed in the final stage of relay contact engagement whereby an appreciable potential energy is stored in such flexed elements. Therefore, as seen in FIGURE 5, when the switch 27 is opened to remove the flow of load current through the auxiliary coil section of the coil 10, potential energy of the flexed elements imparts a counterclockwise movement to the movprovided by the energy of the flexed elements :14 and 21 in contact closed condition must exceed the torque on the moving coil system provided by the magnetic attractionof the closed magnetic contacts 17 and '18, if the relay is to reset upon breaking of the load current circuit. For this reason, a system is employed in which the magnetic attraction of theelements 17 and 18 is relatively weak compared to the attraction between magnetic contact elements of prior art relays. The magnetic contact closure does provide for a reliable initial contact which functions well at very low voltages; i.e. voltages at which the usual loadcurrent-contact-aiding type system, per se, does not function well.

Having now described my invention in detail in accordance with the patent statutes, various changes and modifications will suggest themselves to those skilled in this art. For example, it will be apparent that instead of providing the magnetic contact element 17 with a flexible mounting, the associated magnetic contact element-18 may be flexibly mounted instead. An instrument embodying such a modified version of my invention is illustrated in FIGURE 6 of the drawings. Referring, then, to FIGURE 6, it will be noted that the pointer shaft 14 comprises a relatively rigid, or stiif, member which includes no flexible portion. The flexible contact element 2.1 is secured to the pointer 14' by welding, or any other suitable manner.

The magnetic contact element, or rider, 17 on the pointer 14' cooperates with the magnetic contact element 18 which element, in the modified arrangement of FIG- URE 6, is resiliently mounted by means of the spring means 31. The operation of the instrument is substantially the same as that described above. That is, in mak-' ing of the contacts, the magnetic contacts preferably close first, or simultaneously with the contact elements 21 and 22. The impact engagement of the contacts 17 and 18 provide a good initial contact closure whereupon a loadcurrent-contact-aiding current is supplied to the coil 10. The resultant additional torque on the moving coil system serves to further rotate the moving coil system and thereby flex, or bend the flexible mounting 31 and, at the same time, to effect a wiping or scraping action closure of the flexible contact element and fixed contact element '22, It is intended that the above and other such changes and modifications, such 'as the flexible mounting of the contact 22 instead of the contact 21, shall fall within the spirit and scope of the invention as recited in the following claims.

I claim:

1. A load-current-contact-aiding type instrument including a movable contact element and associated stationary 4. In an instrument type relay, a moving system including a rotatable coil means, a source of control current for said means, a contact arm rotatable with the said coil, stationary magnetic contact element, a movable magnetic contact element carried by said arm for engagement with the said stationary magnetic contact element, one of the said magnetic contact elements being of magnetic material and the other of magnetized material, a flexible contact element carried by said arm, a stationary contact element adapted for cooperation with the said flexible contact ele- 6 ment, and means applying an aiding torque to said moving system upon closure of the said magnetic contact elements to further rotate the moving system and thereby provide a wiping contact engagement between the said flexible contact element and the associated stationary contact element.

5. The invention as recited in claim 4 wherein the said arm includes end portions of predetermined stiflness connected by a connecting portion of greater flexibility, the said movable magnetic contact element being secured to the outer end portion of the arm and the said flexible contact element being secured to the inner end portion of the arm.

6. The invention as recited in claim 5 wherein the said arm and flexible contact element are flexed in the closed condition of the relay contact elements, the potential energy of the above flexed arm and element being of sufficient magnitude to break the contact engagement upon removal of the aiding torque to the moving system.

7. The invention as recited in claim 4 wherein the movable contact elements engage the associated stationary contact elements substantially simultaneously.

8. The invention as recited in claim 4 wherein the engagement of the closed contact elements is broken upon removal of the said means applying an aiding torque to I said moving system therefrom.

9. In an instrument type relay, a moving system including a rotatable coil means which includes a control coil element and auxiliary coil element, the said control coil being adapted to be connected to a source of control current, a contact arm rotatable with said coil, a stationary magnetic contact element, a movable magnetic contact element carried by the said arm for engagement with said stationary magnetic contact element, one of said magnetic contact elements being of magnetic material and the other of magnetized material, a flexible movable contact element secured to the said contact arm, the said contact arm including a flexible portion between the said movable contacts elements secured thereto, means including the said auxiliary coil winding for producing an aiding-contactclosing torque on the moving system to flex the flexible movable contact element and the flexible contact arm in the closed condition of the relay, thepotential energy of the flexed movable contact arm and flexible contact element producing a counter torque to said moving system to develop a force for resetting said contacts when the aidingcontact-closing torque producing means is,removed from the said moving system.

10. In an instrument type relay, a moving system including a rotatable coil means adapted to be connected to a source of control current, a contact arm rotatable with the said coil, a stationary magnetic contact element, a mov- .able magnetic contact element carried by said arm for engagement with the said stationary magnetic contact element, one of the said magnetic contact elements being of magnetic material and the other of magnetized material, means flexibly mounting at least one of the said magnetic contact elements, means applying an aiding torque to said moving system upon closure of the said magnetic contact elements to further rotate the moving system and thereby flex the said flexible mounting means, the resultant energy stored in the flexible. mounting means being suflicient to break the connection between the said magnetic contact elements upon removal of the said aiding torque to the said moving system.

11. A load-current-electrical-contact aiding type instrument including a first pair of contacts consisting of a mov-' able electrical contact element and an associated stationary electrical contact element, a magnetic electrical contact system including movable magnetic and fixed magnetic electrical contact elements one of which is flexibly mounted, forming a second pair of contacts, the said second pair of contact elements being constructed to close with the first pair of contact elements to establish parallel electrical paths between said pairs of electrical contacts.

7 t 12. A load-current-electrical-contact-aiding type instru- References Cited in, the file of this patent ment including a movable electrical contact element and associated stationary electrical contact element one of UNITED STATES PATENIS which is flexiby mounted, forming a first pair of contacts, 1,412,451 Collins Apr. 11, 1922 a magnetic electrical contact system including movable 5 2,039,230 Lamb Apr. 28, .1936 magnetic and fixed magnetic electrical contact elements, 2,464,886 OReilly Mar. 22, 1949' forming a second pair of contacts, the said second pair of 2,494,622 Lamb Jan. 17, 1950 contact elements being constructed to close With the said 2,502,159 Lamb et al. Mar. 28, 1950 first pair of contact elements to establish parallel electrical 2,515,314 Pierce July 18, 1950 paths between said pairs of electricalcontacts. 10 2,658,179 Eadie Nov. 3, 1953 

